The objective of the research proposed here is to quantify the contribution of sensory and nonsensory variables to alterations produced by some narcotic analgesics in the discrimination of an environmental stimulus which potentially may be "painful." By examining the contribution of several variables to the effects of the narcotic analgesics, a profile of drug-induced alterations in the discrimination of environmental stimuli should emerge. Our major consideration will be the measurement of the degree to which alterations in behavior under the control of a discriminative stimulus reflect changes in sensitivity as opposed to factors that affect response bias. To meet this goal we will use two procedures which allow us to manipulate sensory and nonsensory variables and thereby examine the extent to which these variables determine a drug's effect. A shock titration procedure will be used to examine the intensity of electric shock animals will tolerate under conditions in which the stimulus and the response aspects of the task are manipulated. In the order procedure, electric shock will be employed as a discriminative stimulus and both the sensory (or stimulus) and the nonsensory (or response) aspects of the discrimination will be examined with a signal detection analysis. The effects of several narcotic and narcotic antagonist analygesics (morphine, meperidine, pentazocine) will be examined as well as combinations of morphine and amphetamine. The effects of diazepam and chlorpromazine will be examined for comparative purposes.